1. Field of the Invention
This invention relates to an improved blood oxygenator, and more specifically, to an oxygenator having a plurality of uniquely configured oxygenator tubes.
2. Prior Art
Blood oxygenators are well recognized in the prior art. In such devices, the oxygenator functions so as to enable oxygen gas to contact blood such that the oxygen reacts with the hemoglobin in the blood with the resultant absorption of the oxygen into the blood and the release of carbon dioxide therefrom. Examples of such prior art oxygenators are disclosed in U.S. Pat. Nos. 3,768,977; 3,769,162; 3,769,163; 4,067,696; and 3,547,591. Other examples of oxygenators are those sold by William Harvey Research Corporation under the designations "Hybrid Disposable Oxygenator Model H-1000 and Model H-1100". With respect to the two Harvey units, multiple, small diameter oxygenator tubes are provided in a patterned parallel array. A base header plate secures the patterned array of oxygenator tubes at the bottom thereof, and a top header plate secures the oxygenator tubes at the top thereof. A tubular boundary case surrounds and secures the base header plate, the top header plate and the multiple oxygenator tubes in a specific configuration. Heat transfer fluid conduits are disposed through the boundary case such that heat transfer fluid can flow into and out of the case heating the tubes, but without any mixing of the blood and heat transfer fluid.
In the operation of the Harvey devices, a two-phase blood-oxygen gas mixture circulates upward through the multiple oxygenator tubes and a temperature controlled heat transfer fluid circulates exterior to the tubes through the tubular boundary case. The two-phase blood-oxygen flow in the oxygenator is formed with a minimum of turbulence and damage to the blood by providing a specifically configured blood-oxygen manifold. The manifold includes a blood manifold and an oxygen manifold configured such that a plurality of oxygen bubbles are readily infused into the blood as it flows through the oxygenator. The case is circumferentially surrounded by a diffusor made of reticulated polyurethane foam which further oxygenates the blood as it exits out of the tubular boundary case. An outer defoamer layer of treated polyurethane is circumferentially disposed about the tubular case and the diffusor such that when the blood foam contacts such defoamer the blood foam bubbles collapse.
While such units have been found to be useful in the extra-corporeal treatment of blood, a number of shortcomings are believed to exist. One is the fact that as the blood is introduced into the oxygenator, some of the tubes are thought to permit more blood to flow therethrough than others. This is believed to be due to the creation of varying pressures adjacent the bottom of the tubes. Because of this problem, care must be exercised to insure that the blood is being sufficiently oxygenated. Usually, more oxygen is pumped through the blood than may otherwise be necessary to compensate for any flow irregularities. The problem is that the contact between by the oxygen on the blood is believed to cause hemolysis, i.e. a breakdown of the red blood cells.
The present invention is directed to an oxygenator which incorporates uniquely configured oxygenator tubes. These tubes are specifically arranged and configured such that problems of varying flow rates through different oxygenation tubes is substantially overcome. In addition, because the efficiency of each tube is greater than in prior Harvey units, the number of tubes necessary can be decreased. By the use of the oxygenator of the present invention, improvements in heat exchange, oxygen transfer rate and dynamic priming volume can be achieved. Other advantages of the oxygenator of the present invention are discussed in greater detail hereinbelow.